The world is turning into an aging society as the birth rate of the human population has decreased with the increased the average life span. Meanwhile, it is more important to accurately diagnose and effectively prevent and treat complicated disorders such as adult diseases and chronic diseases since fat as the human population suffering from obesity and adult diseases increases. Since a biomolecule, that is, a biomarker, which is an important factor used to diagnose disorders is generally present at a very low concentration in the human body or a test sample, there is a need for methods for detecting the biomolecule with ultrahigh sensitivity. Many measurement methods known up to now have excellent sensitivity, but have the following problems which are short of performance or should be improved further:
(1) Are they used as a method for amplifying biological signals which may be generally used in the art, as well as signals of certain disorders, certain test samples, etc.?
(2) Are they easily used in experimental methods?
(3) It is easy to avoid the amplification of false signals caused by the non-selective absorption?
(4) Is there no problem in aspect of the costs used to perform a large number of experiments?
These factors are important in precisely analyzing a limited amount of a test sample and accurately diagnosing the assay results. Therefore, in order to overcome the difficulty in the existing analytic methods such ELISA, in which one marker molecule should be analyzed one by one, there is increasing demand for the development of measurement methods which may be used to compare and analyze various marker molecules for diseases at a time.
Mass spectrometry is a method in which biomolecules such as nucleic acids, proteins, peptides and sugars may be used to accurately determine the kind and amount of a common organic compound to be analyzed by measuring the molecular weight and signal intensity of the target molecule. In theory, the mass spectrometry has a broad range of available molecules since it is used without regard to the presence of certain functional groups. Also since the mass spectrometry may often be used to exactly analyze various kinds of target molecules in a complicated test sample at a time, it is, for example, possible to analyze and diagnose various disease marker molecules.
Several kinds of the mass spectrometry are present according to the ionization of a test sample and the detection of ions. Among them, matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry has been widely used for the mass spectrometry of test biosamples. The MALDI-TOF mass spectrometry has been known as a method most suitable for ultrahigh-throughput diagnosis in which a large number of test samples should be diagnosed rapidly. However, the MALDI-TOF mass spectrometry has a problem in that when it is used to directly measure a molecular weight of a target molecule, its sensitivity is very deteriorated, which makes it difficult to measure a small amount of a biomarker. Also, it is difficult to obtain information on the presence of a biomarker and an amount of the biomarker using the MALDI-TOF mass spectrometry. Therefore, in order to solve the above-mentioned problems, the development of high-sensitive quantitative MALDI-TOF mass spectrometry, and the further development of signal-amplifiable mass spectrometry which can be used to quantitatively analyze a trace of biomolecule are absolutely required.